Small electric motors are used for many purposes in automobiles. For example, a fully equipped automobile includes individual motors for powering each windshield wiper system, fan, and window lift system and three additional motors for powering each adjustable seat. Electric motors are also used as sunroof, mirror, and antenna drives.
Ordinarily, these motors have metal housings that are formed from drawn steel cans. C-shaped permanent magnets are attached to the sides of the can with adhesives, clips, or screws that are tapped into the magnets. The steel body of the can functions as a flux ring surrounding the magnets. A self-centering bearing is mounted at a closed end of the can. One end of an armature shaft is journaled in the bearing, and the armature shaft can be tilted with the bearing into alignment with another bearing carried in a housing cover.
The drawn steel cans are expensive and add considerable weight to the motors. The self-centering bearings also add cost and require additional clearance between the armature and the permanent magnets to align the armature shaft between the bearings. The additional clearance detracts from motor performance.